The invention concerns a fixing for implantable electrodes and catheters.
Active electronic implants for functional electrostimulation (FES) generally have to be anchored at the location of use in order to retain their position in the tissue, which is wanted for therapy or diagnosis, over time. That is particularly important for implantable electrodes or for catheters which are fitted over a prolonged period of time and which are arranged in a moving organ matrix, for example in the heart. A large number of very different solutions have been developed for fixing purposes. Electrodes or catheters involving passive fixing (for example barb-like anchor systems consisting of the insulation material of the electrode/catheter) are distinguished from those involving active fixing (for example a screw system at the electrode head). The former are particularly suitable for anchoring in the greatly subdivided surface of the right ventricle (trabecula structure), while the latter are particularly suitable for anchoring in the smoother right atrium. All known fixings are formed from materials which are as biocompatible and bioresistant as possible (do not break down in vivo).
For use in the appropriate fashion, the electrodes/catheters are firstly positioned at the desired location in the body of the patient, anchored with suitable means and then remain in the predetermined position for a given period of time depending on the respective therapeutic or diagnostic task. After conclusion of the therapy/diagnosis or for other reasons (for example changing the battery) the electrode/catheter has to be removed again. Accordingly, very different requirements in relation to time are to be made on the fixing.
A fixing which is bulky or which already develops high levels of holding force is undesirable during positioning of the electrode/catheter as that impedes positioning and also repositioning (for the correction of defective positioning) and can result in tissue damage. That problem arises in particular in relation to passive fixings.
In addition, the holding force of the fixing changes with an increasing residence time of the implantable electrode/catheter in the body due to its gradually growing into position. Thus the holding force can still be relatively low shortly after positioning so that there is the risk of unwanted repositioning thereof. In contrast, after a prolonged residence time in the body, the electrodes/catheters can no longer be removed without major interventions for the holding forces between the fixing and the tissue environment also increase with the electrodes/catheters increasingly growing into place.